Method of applying a photosensitive resin to a substrate for use in papermaking

ABSTRACT

The invention comprises a method for applying a curable resin, such as a photosensitive resin, to a substrate such as a papermaker&#39;s dewatering felt. The method comprises the steps of providing a substrate; providing a curable liquid resin; providing a second material different from the curable liquid resin; applying the second material to the substrate to occupy at least some of the voids in the substrate intermediate the first and second surfaces of the substrate; applying the curable resin to the substrate; curing at least some of the resin to provide a resin layer on the substrate; and removing at least some of the second material from the substrate, wherein at least some of the second material is removed from the substrate after applying the curable resin to the substrate.

This is a continuation of application Ser. No. 08/388,948, filed on Feb.15, 1995, now abandoned.

FIELD OF THE INVENTION

The present invention provides a method for applying a curable resin toa substrate, and more particularly, to a method of applying aphotosensitive resin to a substrate to form a web patterning apparatusfor use in papermaking.

BACKGROUND OF THE INVENTION

The application of coatings, such as resin coatings and foam coatings tosubstrates is known in the papermaking art. For instance, it is known toapply a photosensitive resin to a foraminous member in a preselectedpattern for use in a papermaking operation. It is also known to providepapermaking press fabrics with a coating, such as a foam coating, toachieve a controlled void volume and permeability. The followingdocuments describe the use of resins, fillers, foams, layeredconstructions, or other coatings in making papermaking equipment: U.S.Pat. No. 3,549,742 issued Dec. 22, 1970 to Benz; U.S. Pat. No. 4,446,187to Eklund; U.S. Pat. No. 4,514,345 issued Apr. 30, 1985 to Johnson etal.; U.S. Pat. No. 4,637,859 issued Jan. 20, 1987 to Trokhan; U.S. Pat.No. 4,795,480 issued Jan. 3, 1989 to Boyer et al.; U.S. Pat. No.5,098,522 issued Mar. 24, 1992 to Smurkoski et al.; U.S. Pat. No.5,346,567 issued Sep. 13, 1994 to Barnewall; U.S. Pat. No. 5,334,289issued Aug. 2, 1994 to Trokhan et al.; and PCT Publication Number WO91/14558 published Oct. 3, 1991 in the name of Sayers et al. andassigned to the SCAPA Group.

It is also known to impregnate textile fabrics, such as needled fibermats and felt material, with resins and filler materials. The followingdocuments describe the use of resins and/or fillers in fabrics: U.S.Pat. No. 4,250,172 to Mutzenberg et al; U.S. Pat. No. 4,390,574 to Wood;U.S. Pat. No. 4,464,432 to Dost et al.; U.S. Pat. No. 5,217,799 to Sumiiet al.; U.S. Pat. No. 5,236,778 to Landis et al.; and Reissue Pat. No.32,713 reissued Jul. 12, 1988 to Woo.

After curing a portion of the resin on a substrate to form a papermakingapparatus, it is desirable to remove uncured resin from the substrate.Removal of uncured resin from the substrate is important so that theresulting papermaking apparatus has the desired characteristics for itsparticular papermaking application. Such characteristics can include,but are not limited to, flexibility of the apparatus, compressibility ofthe apparatus, air permeability through the apparatus, and waterpermeability through the apparatus. Removal of uncured resin isespecially important in a papermaking apparatus having a patterned resinsurface with openings through which air and/or water is conveyed duringformation or drying of the paper web. Uncured resin remaining in thesubstrate can reduce the permeability of the substrate, and therebyreduce flow through the openings in the patterned resin surface.

One method for removing uncured resin includes washing uncured resinfrom the substrate. For instance, above referenced U.S. Pat. No.4,514,345 discloses washing uncured resin from a foraminous memberformed of woven filaments, followed by vacuuming of residual wash liquidand uncured liquid from the foraminous member. However, washing andvacuuming, alone, can be ineffective in removing all uncured resin.

A felt or open celled foam substrate can have a large number ofrelatively small, internal void cavities which can trap uncured resin.Such trapped uncured resin can degrade the performance of thepapermaking apparatus, as described above. In addition, such trappedresin is essentially wasted, adding to the cost of the resin castingprocess. Removal of the trapped resin by increasing the number ofwashing and vacuum cycles also increases the cost of the process.

Moreover, in some applications it may be desirable to control the depthof penetration of the resin into the substrate. For instance, it may bedesirable to have the cured resin layer penetrate a predeterminedportion of the thickness of the substrate, so as to provide acceptablebonding of the resin to the substrate, while maintaining the flexibilityof the substrate and the permeability of the substrate to air and water.

U.S. Pat. No. 3,549,742 issued Dec. 22, 1970 to Benz discloses insertingfilling material into apertures in a drainage member which willultimately be open for drainage, after which a settable material isinserted into the remaining apertures of the drainage member in thepredetermined areas in which flow of liquid through the drainage memberis to be prevented. The settable material is fixed or cured, after whichthe filling material is removed from the drainage member. Benz has thedisadvantage that the filler material is arranged in a predeterminedpattern prior to application to the drainage member, and the fillermaterial must be pressed into the drainage member such thatpredetermined areas of the drainage member member are left free of thefilling material. Accordingly, the pattern in which the settablematerial can be fixed to the drainage member is limited by thepredetermined areas of the drainage member left free of the fillingmaterial.

Also, Benz uses pressure to mechanically force the filler material intothe drainage member. Pressing a filling material into a substrate cansuffer from the disadvantage that, if the substrate has many smallinternal voids, and is relatively compressible, applying pressure to thesubstrate can collapse the substrate or close some of the voids in thesubstrate, thereby making penetration of the substrate by the fillermaterial difficult.

In addition, pressing a filling material into a felt layer can result inthe filling material flowing laterally into areas of the felt which aremeant to be left open for the settable material. Therefore, the methoddisclosed by Benz is undesirable for use in applying a curable resin toa felt layer.

Accordingly, one object of the present invention is to provide a methodof applying a curable resin to a substrate to form a papermakingapparatus.

Another object of the invention is to provide a method for reducing theamount of uncured photosensitive resin that is required to be removedfrom a paper web patterning apparatus suitable for making paper havingvisually discernible patterns.

Another object is to provide a method for forming a web patterningapparatus having a dewatering felt layer and a patterned photosensitiveresin layer which penetrates a surface of the felt layer and extendsfrom the surface of the felt layer.

SUMMARY OF THE INVENTION

The invention comprises a method of applying a curable resin to asubstrate. In particular, the method can be used to form a papermakingapparatus such as a paper web forming fabric or a paper web dryingfabric. In one embodiment, the method of the present invention can beused to apply a photosensitive resin to a dewatering felt layer toprovide a papermaking apparatus that can be used to pattern and dewatera paper web. The resulting papermaking apparatus can comprise adewatering felt layer having a first web facing felt surface at a firstelevation and a second oppositely facing felt surface, and a webpatterning layer comprising the photosensitive resin. The patterninglayer penetrates the first felt surface, and extends from the first feltsurface to form a web contacting top surface at a second elevationdifferent from the elevation of the first felt surface.

The method according to the present invention provides a barrier in thesubstrate to restrict the depth to which the curable liquid resin canpenetrate through the thickness of the substrate. The method comprisesthe steps of:

providing a substrate having a first surface, a second surface, and athickness, the substrate having voids intermediate the first and secondsurfaces;

providing a curable liquid resin;

providing a second material different from the curable liquid resin;

applying the second material to the substrate to occupy at least some ofthe voids in the substrate intermediate the first and second surfaces ofthe substrate;

applying the curable resin to the substrate;

curing at least some of the resin to provide a resin layer on thesubstrate; and

removing at least some of the second material from the substrate,wherein at least some of the second material is removed from thesubstrate after applying the curable resin to the substrate.

The step of removing at least some of the second material preferablycomprises removing at least about 50 percent of the second materialapplied to the substrate, and more preferably, removing substantiallyall of the second material applied to the substrate.

In one embodiment the substrate comprises a papermaker's dewateringfelt, and the resin comprises a photosensitive resin.

In one embodiment, the method includes the steps of reducing themobility of the second material applied to the substrate prior toapplying the resin to the substrate. The method can also include thestep of increasing the mobility of the second material after curing atleast some of the resin, to thereby facilitate removal of the secondmaterial from the substrate.

In one embodiment, the method can include the step of changing the phaseof the second material applied to the substrate prior to applying theliquid photosensitive resin. In one embodiment the second material isapplied throughout the thickness of the substrate as a liquid mixture ofwater and a soap gelling agent. The second material is cooled to hardenthe second material to a gel phase. A thin layer of the gelled secondmaterial adjacent to the first surface of the substrate is liquified orsolubilized for removal by water showering to provide a portion of thethickness of the substrate adjacent to the first surface which issubstantially free of the second material.

The liquid photosensitive resin can then be applied to the first surfaceof the substrate to penetrate into the substrate from the first surface,and to extend outward of the substrate a predetermined distance from thefirst surface. A source of actinic radiation and a mask having opaqueand transparent regions are provided. The liquid photosensitive resin iscured in a predetermined pattern by exposing the resin to the actinicradiation through the mask. Uncured liquid resin can then be washed fromthe first surface of the substrate with water showering. The gelledsecond material remaining in the substrate is then liquified and removedfrom the substrate by heating, hot water showering and vacuuming.

DESCRIPTION OF THE DRAWINGS

While the Specification concludes with claims particularly pointing outand distinctly claiming the present invention, the invention will bebetter understood from the following description taken in conjunctionwith the associated drawings, in which like elements are designated bythe same reference numeral, and:

FIG. 1 is a plan view illustration of an apparatus made according to themethod of the present invention, the apparatus including a dewateringfelt layer and a cured photosensitive resin web patterning layer joinedto the dewatering felt layer and having a continuous network webcontacting top surface.

FIG. 2 is a cross-sectional illustration of the apparatus in FIG. 1.

FIG. 3 is an illustration of a process for making paper with a webpatterning apparatus made according to the method of the presentinvention.

FIGS. 4A-4H are schematic illustrations of steps for making a webpatterning apparatus according to the method of the present invention.

FIG. 5 is a schematic illustration of a method according to the presentinvention for making a web patterning apparatus having a felt dewateringlayer and a web patterning layer formed from photosensitive resin.

FIG. 6 is a photomicrograph of an apparatus made according to the methodof the present invention.

FIG. 7 is a photomicrograph of a cross-section of the apparatus of FIG.6.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 are illustrations of a papermaking web support apparatus200 which can be made using the method of the present invention. Theapparatus 200 can comprise a substrate, such as a dewatering felt layer220, and a cured resin web patterning layer 250 joined to a surface ofthe felt layer 220. FIG. 3 illustrates a process for making a paper webusing the apparatus 200 shown in FIGS. 1 and 2. FIGS. 4A-4H illustratesteps according to the present invention for making a web patterningapparatus 200 by curing a photosensitive resin on a surface of asubstrate. FIG. 5 is a schematic illustration of one embodiment of themethod of the present invention. FIGS. 6 and 7 are photomicrographs ofan apparatus 200 made using the method of the present invention.

The Web Support Apparatus

FIGS. 1, 2, and 4H show a web support apparatus 200, which can comprisea continuous drying belt for drying and imparting a pattern to a paperweb. The web support apparatus 200 has a first web facing side 202 and asecond oppositely facing side 204. The web support apparatus 200 isviewed with the first web facing side 202 toward the viewer in FIG. 1.

The web support apparatus 200 includes a substrate having voidsintermediate first and second surfaces of the substrate. At least someof the voids are preferably in flow communication with at least one ofthe surfaces of the substrate. For instance, the substrate can comprisea dewatering felt layer 220 having a first web facing felt surface 230disposed at a first elevation 231 (FIG. 2), and an oppositely facingsecond felt surface 232. The felt layer 220 has a plurality of voidsintermediate the first surface 230 and the second surface 232. The websupport apparatus 200 also comprises a web patterning layer 250 joinedto the first web facing surface 230. The web patterning layer 250extends from the first felt surface 230, as shown in FIG. 2, to have aweb contacting top surface 260 at a second elevation 261 different fromthe first elevation 231. The difference 262 (FIG. 4H) between the firstelevation 231 and the second elevation 261 can be at least about 0.05millimeter, and in one embodiment is between about 0.1 and about 2.0millimeters.

The dewatering felt layer 220 is water permeable and is capable ofreceiving and containing water pressed from a wet web of papermakingfibers. The web patterning layer 250 is water impervious, and does notreceive or contain water pressed from a web of papermaking fibers. Theweb patterning layer 250 can have a plurality of discrete openings 270therethrough, and form a continuous network on the first felt surface230, as shown in FIG. 1. Alternatively, the web patterning layer can bediscontinuous, or semicontinuous.

The web patterning layer 250 comprises a curable resin which can bedeposited on a surface of a substrate as a liquid, and subsequentlycured so that a portion of the web patterning layer penetrates a surfaceof the substrate. In particular, the web patterning layer 250 cancomprise a photosensitive resin which can be deposited on the firstsurface 230 as a liquid and subsequently cured by radiation so that aportion of the web patterning layer 250 penetrates, and is therebysecurely bonded to, the first felt surface 230. The web patterning layer250 preferably does not extend through the entire thickness of the feltlayer 220, but instead extends through less than about half thethickness of the felt layer 220 to maintain the flexibility andcompressibility of the web support apparatus 200, and particularly theflexibility and compressibility of the felt layer 220.

A suitable dewatering felt layer 220 comprises a batt 240 of natural orsynthetic fibers joined, such as by needling, to a support structureformed of woven filaments 244, as shown in FIG. 4A. Suitable materialsfrom which the batt 240 is formed include but are not limited to naturalfibers such as wool and synthetic fibers such as polyester and nylon.The fibers from which the batt 240 is formed can have a denier ofbetween about 1 and 20 grams per 9000 meters of filament length.

The felt layer 220 can have a layered construction, and can comprise amixture of fiber types and sizes. The felt layer 220 can have finer,relatively densely packed fibers disposed adjacent the first feltsurface 230. In one embodiment, the felt layer 220 can have a relativelyhigh density and relatively small pore size adjacent the first feltsurface 230 as compared to the density and pore size of the felt layer220 adjacent the second felt surface 232.

The dewatering felt layer 220 can have a thickness of between about 2millimeters and about 5 millimeters, a basis weight of between about 800and about 2000 grams per square meter, an average density (basis weightdivided by thickness) of between about 0.16 gram per cubic centimeterand about 1.0 gram per cubic centimeter, and an air permeability ofbetween about 5 and about 300 standard cubic feet per minute (scfm),where the air permeability in scfm is a measure of the number of cubicfeet of air per minute that pass through a one square foot area of thefelt layer 220 at a pressure drop across the thickness of the felt layer220 equal to about 0.5 inch of water. The air permeability is measuredusing a Valmet permeability measuring device (Model Wigo Taifun Type1000) available from the Valmet Corp. of Pansio, Finland. Thepermeability of the web support apparatus 200 is less than or equal tothe permeability of the felt layer 220 and is about equal to thepermeability of the felt layer 220 multiplied by the fraction of theprojected area of the apparatus 200 not covered by the web patterninglayer 250.

A suitable felt layer 220 is an Amflex 2 Press Felt manufactured by theAppleton Mills Company of Appleton, Wis. Such a felt layer 220 can havea thickness of about 3 millimeter, a basis weight of about 1400gm/square meter, an air permeability of about 20 to 30 scfm, and have adouble layer support structure having a 3 ply multifilament top andbottom warp and a 4 ply cabled monofilament cross-machine directionweave. The batt 240 can comprise nylon fibers having a denier of about 3at the first surface 230, and denier of between about 10-15 in the battsubstrate underlying the first surface 230.

Suitable photosensitive resins are disclosed in U.S. Pat. No. 4,514,345issued Apr. 30 1985 to Johnson et al. and U.S. Pat. No. 5,334,289 issuedAug. 2, 1994 to Trokhan et al., which patents are incorporated herein byreference. The resin, when cured, can have a hardness of less than orequal to about 60 Shore D. The hardness is the average of fivemeasurements on an unpatterned photopolymer resin coupon measuring aboutI inch by 2 inches by 0.025 inches thick cured under the same conditionsas the web patterning layer 250. The hardness measurements are made at25 degrees Centigrade and read 10 seconds after initial engagement ofthe Shore D durometer probe with the resin. A resin having such ahardness upon curing is desirable so that the web patterning layer 250is somewhat flexible and deformable. The cured resin preferably resistsoxidation. The uncured resin can have viscosity of between about 5000and about 25000 centipoise at 70 degrees Fahrenheit to facilitatepenetration of felt layer 220 by the resin prior to curing. Suitableliquid photosensitive resins included in the Merigraph series of resinsmade by Hercules, Inc. of Wilmington, Del. incorporating an antioxidantas disclosed in above referenced U.S. Pat. No. 5,334,289. A suitableliquid photosensitive resin is a MEH-1000 resin available from Hercules,Inc.

Use of the Web Support Apparatus to Make Paper

FIG. 3 illustrates use of the apparatus 200 in making a paper web 20. Aslurry of papermaking fibers, such as cellulosic wood pulp fibers, isdeposited from a headbox 500 onto a foraminous, liquid pervious formingbelt 542, to form an embryonic web of papermaking fibers 543 supportedby the forming belt 542. The forming belt 542 can comprise a continuousFourdrinier wire, or alternatively, can be in the form of any of thevarious twin wire formers known in the art. The web 543 is thentransferred from the forming belt 542 to the web support apparatus 200,with the embryonic web 543 positioned on the first side 202 of the websupport apparatus 200.

The step of transferring the embryonic web 543 to the web supportapparatus 200 can simultaneously include the step of deflecting aportion of the web 543 into openings 270 in the web patterning layer 250to form a non-monoplanar web 545. The steps of transferring theembryonic web 543 to the web support apparatus 200 and deflecting aportion of the embryonic web 543 can be provided, at least in part, byapplying a differential fluid pressure to the embryonic web 543 by avacuum source 600. One or more additional vacuum sources 620 can also beprovided downstream of the embryonic web transfer point.

After transferring and deflecting the embryonic web 543 to form thenon-monoplanar web 545, the web 545 is carried on the web supportapparatus 200 through a nip 800 provided between a yankee drying drum880 and a roller 900. The web is transferred to and dried on the surface875 of the drum 880, and then creped from the surface 875 by a doctorblade 1000 to form a creped paper web 20. Prior to transferring the web545 to the drying drum 880, the web can be further dewatered, such as bypressing or by through air drying. For instance, the web can be pressedin a press nip 700 between the web support apparatus 200 and a separatedewatering felt 712, as is disclosed in U.S. patent application Ser. No.08/358,661 "Wet Pressed Paper Web and Method of Making the Same" filedDec. 19, 1994 in the name of Ampulski et at. The following patentdocuments are incorporated herein by reference in their entirety for thepurpose of disclosing how to make a patterned web 20: U.S. Pat. No.4,529,480 issued Jul. 16, 1985 to Trokhan; U.S. patent application Ser.No. 08/268,154 "Web Patterning Apparatus Comprising a Felt Layer and aPhotosensitive Resin Layer" filed Jun. 29, 1994 in the Name of Trokhanet al.; U.S. patent application Ser. No. 08/268,213 "Paper StructuresHaving at Least Three Regions Including a Transistion RegionInterconnecting Relatively Thinner Regions disposed at DifferentElevations, and Apparatus and Process for Making the Same" filed Jun.29, 1994 in the name of Trokhan et al.; and U.S. patent application Ser.No. 08/358,661 "Wet Pressed Paper Web and Method of Making the Same"filed Dec. 19, 1994 in the name of Ampulski et at.

Making a Paper Web Support Apparatus with Photosensitive Resin Cured ona Felt Layer

The web support apparatus 200 can be made according to the presentinvention using steps illustrated in FIGS. 4A-4H. A substrate isprovided having a first surface, a second surface, and a thickness, withthe substrate having voids intermediate the first and second surfaces.In FIG. 4A the substrate provided is a dewatering felt layer 220. Aliquid photosensitive resin and a second material different from thephotosensitive resin are also provided.

Referring to FIG. 4B, the present invention includes the step ofapplying the second material, designated by numeral 2000, to the feltlayer 220. The felt layer 220 is conveyed in the direction shown by thearrow in FIG. 4B. In one embodiment, the felt layer 220 can be conveyedadjacent an infrared heating lamp 2310 positioned adjacent the firstfelt surface 230 of the felt layer 220 prior to applying the secondmaterial to the felt layer 220. The heating lamp 2310 can be used towarm the felt layer 220. Use of the heating lamp 2310 is optional, andnot required.

The felt layer 220 can then be conveyed adjacent a header pipe 2410positioned adjacent to the second surface 232 of the felt layer 220. Theheader pipe 2410 has an opening through which the second material 2000is directed onto the second surface 232 of the felt layer 220. Thesecond material is applied as a liquid to the felt layer 220 to occupyat least some voids in the felt layer intermediate the surfaces 230 and232. In FIG. 4B, the second material is applied to the felt layer 200 topenetrate the entire thickness of the felt layer between the surfaces230 and 232. The felt layer 220 on which the second material 2000 hasbeen deposited is directed through a nip 2470 between rollers 2472 toensure that the second material is distributed throughout the entirethickness of the felt layer 220 between the surfaces 230 and 232.Alternatively, the second material 2000 can be applied to the firstsurface 230 of the felt layer 220.

The second material 2000 fills voids in felt layer 220, and therebyprovides a barrier to penetration of the liquid photosensitive resinthroughout the felt layer 220. The second material 2000 serves toprevent the curable resin from entering certain target portions of thevoid-containing felt layer 220. The second material is preferably easilyapplied to the substrate, and is preferably not displaced from the feltlayer 220 by the curable resin. The second material is also preferablyeasily removed from the felt layer 220 after curing of the resin appliedto the felt layer 220.

In one embodiment, the second material 2000 (1) can be applied to thefelt layer 220 in a relatively mobile state to provide penetration ofthe second material 2000 throughout the felt layer 220; (2) can bealtered after it is applied to the felt layer and before application ofthe photosensitive resin to the felt layer 220 to have a reducedmobility to thereby resist displacement of the second material 2000 bythe photosensitive resin; and (3) can be be altered to have an increasedmobility after at least partially curing the resin to facilitate removalof the second material from the voids in the felt layer 220.

In one embodiment, the second material is relatively mobile when firstapplied to the substrate. For instance, the second material can comprisea liquid, a solute disolved in a liquid solvent, solid particlesdispersed in a liquid component of the second material, or a mixture ofliquid reaction components when first applied to the substrate. Afterthe second material has been applied to the substrate, and prior toapplication of the curable resin to the substrate, the second materialis altered to be relatively less mobile than when first applied to thesubstrate, so as to provide a barrier to penetration of the curableresin into predetermined portions of the substrate.

Prior to application of the curable resin to the substrate, the secondmaterial applied to the substrate is preferably transformable to berelatively immobile by, for example: increasing the viscosity of thesecond material; changing the phase of at least a portion of the secondmaterial from a liquid to a solid; evaporating a fluid component of thesecond material to provide an occlusive film or closed cell foam barrierin the substrate; or providing a chemical reaction that transformsliquid reaction components of the second material into highly viscous orsolid reaction products. While FIGS. 4B through 4H will be discussedwith reference to a second material which forms a gel, other examples ofsuitable second materials are provided below.

In one embodiment, the present invention includes the step of changingthe phase of the second material 2000 applied to felt layer 220. Thephrase "changing the phase of the second material" refers to adiscontinuous change in certain properties of the second material at adefinite temperature and pressure. Changing the phase of the secondmaterial includes changing a gas phase of the second material to aliquid or solid phase, changing a liquid phase of the second material toa gas phase or solid phase, and changing a solid phase of the secondmaterial to a gas or liquid phase. Examples of phase changes of thesecond material include, but are not limited to, liquifying the secondmaterial, subliming the second material, and solidifying the secondmaterial by freezing or gelling the second material. In one embodiment,the second material undergoes a phase change from a solid phase to aliquid phase at a temperature below the temperature at which the curedresin degrades (i.e. less than the melting temperature or thedecomposition temperature of the cured resin), and more preferably at atemperature between about 50 degree Fahrenheit and about 150 degreesFahrenheit.

Referring to FIG. 4B, in one embodiment the second material can beapplied to the felt layer 220 as a liquid mixture of water and a gellingagent at an elevated temperature. The liquid mixture of water and thegelling agent can then be allowed to cool on the felt layer 220 to forma solid gel phase of the second material which fills voids in the feltlayer 220.

Prior to applying the photosensitive resin to the felt layer 220, it canbe desirable to remove some, but not all, of the second material fromfelt layer 220 before applying the photosensitive resin to felt layer220. Referring to FIG. 4C, the present invention can include the step ofremoving second material from adjacent the first surface 230 of the feltlayer 220, thereby providing a portion of the thickness of the feltlayer 220 which is substantially free of the second material. Where thesecond material comprises a gel, a layer of the second material adjacentthe first surface 230 of the felt layer 220 can be removed with a watershower 2510. Alternatively, layer of the second material can be removedfrom the felt layer 220 by mechanical brushing. Removing a layer of thesecond material adjacent the first surface 230 provides a predeterminedportion of the thickness of the felt layer 220 to which thephotosensitive resin can be applied and ultimately secured.

Referring to FIG. 4D, the present invention includes the step ofapplying the curable resin to the substrate. In the embodiment shown, alayer 2010 of the liquid photosensitive resin is applied to the exposedfirst surface 230 of the felt layer 220 after some second material isremoved from the surface 230. A mask 3010 is positioned adjacent to thelayer 2010 of liquid resin. The mask 3010 has opaque regions 3012 andtransparent regions 3014. A nip roller 3100 controls the depth d of thelayer 2010 deposited on the felt layer 220. The depth d is selected tobe approximately equal to the desired difference in elevation 262between the surface 260 of the cured resin layer 250 and the feltsurface 230 (FIG. 4G) plus the thickness of the layer of second material2000 removed from the felt layer in FIG. 4C.

Referring to FIG. 4E, the present invention includes the step of curingat least some of the resin applied to the substrate. In one embodimentof the present invention, the resin is selectively cured to provide apatterned resin layer on the substrate. In FIG. 4E, resin curing lamps3150 provide a source of actinic radiation in a first curing step for atleast partially curing the layer 2010 of liquid photosenstive resindeposited on the felt layer 220. The mask 3010 is positionedintermediate the lamps 3150 and the layer 2010 of liquid photosensitiveresin. The liquid photosensitive resin is selectively exposed to theactinic radiation through the mask 3010 to induce curing of thephotosensitive resin in registration with the transparent regions 3014in the mask 3010. The first curing step provides a patterned resin layer250 which is at least partially cured on the first surface 230 of thefelt layer 220.

Referring to FIG. 4F, the present invention can include the step ofremoving uncured resin from the substrate after the first curing stepshown in FIG. 4E. In FIG. 4F, uncured resin is indicated by referencenumeral 2010A. The mask 3010 can be removed from the patterned resinlayer 250. The uncured resin 2010A can then be removed with watershowers 2530. The water showers can be angled to remove uncured resin2010A from the openings 270 in the patterned resin layer 250. Thesolidified second material 2000 prevents the uncured resin frompenetrating through the full thickness of the felt layer 220, andmaintains the uncured resin adjacent the first surface 230 of the feltlayer 220. Accordingly, the uncured resin 2010A is relatively easy toremove from the openings 270 in the resin layer 250 with a water shower2530. Referring to FIG. 4G, the present invention includes the step ofremoving at least some of the second material 2000 from the substrateafter the resin is applied to the substrate. In embodiments where thesecond material 2000 is solidified, such as by gelling, the secondmaterial 2000 can be removed by heating the second material to atemperature above its gelling temperature, thereby liquifying the gelledsecond material. In FIG. 4G, the felt layer 220 is conveyed adjacent aninfrared heating lamp 3170 positioned adjacent the first surface 230 ofthe felt layer 220. The second material 2000 can be heated with infraredheating lamps 3170 to liquify the second material. The felt layer 220can then be washed with a hot water shower 2550, and directed over avacuum box 2570 to remove the liquified second material, as well as anyremaining uncured photosensitive resin. In FIG. 4G, the hot water shower2550 directs a spray against the first surface 230 of the felt layer220. The vacuum box 2570 provides a vacuum at the second surface 232 ofthe felt layer 220 to remove liquified second material from the secondsurface 232. Showering and vacuuming can be repeated, as necessary, toremove the liquified second material from the felt layer 220.

Preferably, at least 50 percent of the second material 2000 applied tothe substrate is removed, and most preferably substantially all of thesecond material 2000 applied to the substrate is removed from thesubstrate. As shown in FIGS. 4C and 4G, the second material can beremoved from the substrate both before and after the liquid resin isapplied to the substrate. In the embodiment shown, more of the secondmaterial is removed after application of the liquid resin to thesubstrate than is removed before the resin is applied to the substrate.

In FIGS. 4F and 4G, the uncured liquid resin is washed prior to removalof the second material remaining on the felt layer 220. Alternatively,all the second material 220 can be removed from the felt layer 220,followed by washing of uncured liquid resin from the felt layer 220.

Referring to FIG. 4H, the method according to the present invention caninclude a post curing step performed after substantially all of theuncured liquid resin 2010A and substantially all of the second material2000 has been removed from the felt layer 220. A source of actinicradiation, such as resin post curing lamps 3180 is positioned above theresin layer 250 to complete curing of the resin layer 250. Removal ofall the second material and all the uncured liquid resin from thesubstrate prior to final curing of the resin layer 250 by lamps 3180 isdesirable to prevent inadvertent curing of resin in portions of the feltlayer 220 where permeability to air and water is desired. The postcuring step can be performed with the resin layer 250 submerged in awater bath 1620 to promote complete reaction of the photosensitiveresin, as described below.

The resulting web support apparatus 200 has a cured resin layer 250which penetrates the first surface 230 of the felt layer 220 to extendintermediate the first and second surfaces 230 and 232. The cured resinlayer 250 also extends from the first surface 230 to have a webcontacting top surface 260 at a second elevation different from theelevation of the first surface 230.

Examples of Second Materials for Filing Voids in the Substrate

A number of materials are suitable for use as second material 2000 forfiling voids in the substrate to prevent penetration of the liquid resinthroughout the thickness of the substrate. Preferably, the secondmaterial is added to the substrate prior to application of the liquidresin to the substrate. However, in alternative embodiments the secondmaterial could be applied to a substrate to displace liquid resin thathas been previously applied to the substrate. The following examples aremeant to be illustrative but not limiting.

In one embodiment the second material can comprises water. Where wateris used as the second material 2000, it is preferred that distilledwater is used to prevent hard water deposits on the substrate. Forexample, water can be added to the felt layer 220 as a liquid, andmaintained as a liquid throughout the steps of adding and curing theliquid photosensitive. Maintaining the water as a liquid while addingthe liquid curable resin to the substrate has the disadvantage thatsome, if not most of the water can be displaced by the liquid resinbefore the resin is cured.

In another embodiment, water can be added to the felt layer 220 as aliquid, and then frozen prior to addition of the liquid photosenstiveresin. Changing the phase of the water by freezing the water can providea layer of ice in the felt layer that prevents penetration of the liquidresin throughout the thickness of the felt layer 220.

In another embodiment, the second material can be transformed to have asubstantially increased viscosity as compared to its viscosity whenfirst applied to the felt layer 220. By substantially increase theviscosity of the second material, it is meant that the viscosity of thesecond material increases by a factor of at least 10, and preferably atleast 100. For example, the second material can comprise a solvent and asolute, such as a mixture of water and a solute component which issoluble in water. The water soluble component can comprise a watersoluble resin such a polyvinyl alcohol, applied to the felt layer at anelevated temperature and low solids content. By "soluble in water" it ismeant that a component is soluble in deionized water at 25 degreeCentigrade at a level of at least about 1.0 percent.

Specifically, the second material can include an 8 percent by weightsolution of Elvanol HV (available from Dupont Company, Wilmington, Del.)in water. The second material can be applied to the substrate at atemperature of about 160 degrees Fahrenheit. Such a solution has aviscosity of about 250 centipoise and readily fills the voids in a feltlayer 220. The concentration of the solution can be increased to about14 percent by evaporating water, and the temperature of the solution canbe decreased to about 70 degrees Fahrenheit to increase the viscosity ofthe second material to about 35,000 centipoise. After the photosensitiveresin is applied and cured, the Elvanol can be resolubilized, preferablywith hot water.

In another embodiment, the second material can comprise a water solublegum dissolved in water. Preferred gums show pseudoplastic behavior(shear thinning). "Shear thinning" refers to the reduction of theviscosity of a material when the material is subjected to shear forces.In one embodiment, a 1-3 percent solution of a high viscosity guar gumin water is added to the void containing substrate while the gum andwater solution is subjected to a shear rate and an elevated temperature.At a shear rate in excess of about 10 reciprocal minutes and atemperature of at least about 60 degrees Centigrade the viscosity of thegum and water solution is reduced sufficiently to allow easing fillingof the felt layer 220 with the gum and water solution. The shear rate onthe gum and water solution is then eliminated, and the solution allowedto cool to about 70 degrees Fahrenheit to provide the gum and watersolution with a viscosity greater than or equal to about 50,000centipoise. The increased viscosity of the gum and water solutionprevents displacement of the gum and water solution from the felt layer220 by the curable liquid resin. The "Handbook of Water Soluble Gums andResins," edited by R. L. Davidson, McGraw-Hill, 1980, pp. 6-1 to 6-8 isincorporated herein by reference for the purpose of disclosing suitablewater soluble gums and applying and measuring shear rates.

In another embodiment, the second material can comprise a mixture ofwater and a second component, wherein the water can be removed from themixture, such as by drying or evaporation. For instance, the secondmaterial can be added to the felt layer 220, and the water can beremoved from the second material, such as by evaporation, to provide abarrier to photosensitive resin penetration of the substrate. Thebarrier can then be removed from the substrate by showering thesubstrate with water to wash the barrier from the substrate. Forinstance, the second material can comprise a solution of water and ahigh molecular weight polyvinyl alcohol plasticized with glycerol. Sucha solution can be liquid at about 70 degrees Fahrenheit, and transformsinto a film as the water in the solution evaporates. Suitable polyvinylalcohols include Elvanol 90-50 and Elavanol 71-30 (available from DupontCompany, Wilmington, Del.). A suitable aqueous solution comprises about6-8 percent by weight polyvinyl alcohol. Prior to mixing the polyvinylalcohol in water, the polyvinyl alcohol can be plasticized by forming amixture of about 90 to 95 percent polyvinyl alcohol, and about about 5to 10 percent by weight glycerol. The polyvinyl alcohol and glycerolmixture can then be added to water to form the aqueous solutioncomprising about 6-8 percent by weight polyvinyl alcohol.

In another embodiment, the second material can comprise a soliddispersed in a liquid. For instance, the second material can comprise alow glass transition temperature latex rubber dispersed in water. Thedispersion can comprise about 40 percent by weight poly acrylate latexresin in water. The poly acrylate latex resin can comprise Roplex TR-520poly acrylate latex resin available from the Rohm and Haas Company. Uponevaporation of the water in the dispersion, the solid latex spherescoalesce into a rubbery film that is easily redispersed with waterprovided the temperature of the film is kept below the cross-linkingtemperature of the latex rubber. Alternatively, a blowing agent whichproduces a gas upon heating can be added to the dispersion. Forinstance, diazocarbamide can be added to the latex resin and waterdispersion to produce nitrogen on heating, thereby forming a latex foamupon evaporation of the water in the dispersion.

In one embodiment, the second material can comprise a water soluble waxlike material, such as polyoxyethylene glycol (PEG). PEG can have amelting point below the degradation temperature of the curablephotosensitive resin, such that the second material is a solid at ornear about 70 degrees Fahrenheit, and can be liquified below thedegradation temperature of the curable photosensitive resin. Forinstance, a PEG having a molecular weight in excess of about 600 issuitable. More specifically, the second material can comprise PEG 1500with a melting point of about 46 degrees C., PEG 4000 with a meltingpoint of about 56 degrees C., PEG 6000 with a melting point of about 60degrees C., and mixtures thereof. Alternatively, the second material cancomprise a relatively low molecular weight PEG, such as PEG 400, whichcan remain a liquid during application and curing of the photosensitiveresin.

The second material 2000 can also comprise water soluble surfactants andwater dispersible surfactant systems. For instance, the second materialcan comprise a liquid detergent solution, such as a detergent solutioncomprising anionic and nonionic surfactants, an ethyl alcohol dispensingagent, and water. The detergent solution can be applied to the substrateprior to application of the resin to the substrate. Such a detergentsolution is commercially available as Joy Brand Diswashing Liquid fromthe Procter and Gamble Company of Cincinnati, Ohio.

The second material 2000 can also comprise a water soluble surfactant orwater dispersible surfactant system that is a solid below about 70degrees Fahrenheit. Examples of water soluble surfactants includeanionic derivatives of sulfosuccinic acids. Applied as water solutions,these materials dry to flexible occlusive films suitable to provide abarrier to penetration of the substrate by the liquid photosensitiveresin. An example of an anionic surfactant is Aerosl OT-75 (availablefrom American Cyanimid.) Aerosol OT surfactant is a dioctyl ester ofsodium sulfosuccinic acid.

An example of suitable water dispersible systems includes mixtures oflong chain alkyl quarternary surfactants mixed with polyoxyethyleneglycol 400 or glycerin. More specifically, a mixture of about 70 percentby weight di(touch hardened tallow) dimethyl ammonium chloride withabout 30 percent by weight PEG 400 (which is a pasty wax at about 70degrees Fahrenheit and a liquid at about 150 degrees Fahrenheit) can beused to form the second material 2000.

In another embodiment, the second material can comprise reactioncomponents that are liquid at room temperature or are water soluble andcan be polymerized into a higher molecular weight water soluble solid orhigh viscosity paste. For example, the second material can comprise amixture of about 10 percent by weight acrylic acid, about 20 percent byweight sodium acrylate, about 70 percent water, and a free radicalinitiator. The free radical initiator can be triggered by heat. Anexample of a flee radical initiator is V-50, a 2,2'-Azobis (2-amidinopropane) dihydrochloride available from Wako Chemicals of Dallas Tex.

In another embodiment, the second material can comprise a gelling agent.Suitable gelling agents include, but are not limited to, vegetablegelling agents such as pectin, carrageenan, agar, animal proteingelatins, hydrogel forming polymeric gelling agents, and soap gellingagents. One example of a gelling agent which can be disolved in water toform the second material 2000 is JELLO Brand gelatin from the GeneralFoods Company of White Plains, N.Y.

Suitable hydrogel forming polymeric gelling agents include at leastpartially cross-linked polymers prepared from polymerizable, unsaturatedacid-containing monomers which are water soluble or become water solubleupon hydrolysis. These include monoethylenically unsaturated compoundshaving at least one hydrophilic radical, including olefincallyunsaturated acids and anhydrides which contain at least onecarbon-carbon olefinic double bond. U.S. patent application Ser. No.08/307,951 "Mild Gel Deodorant Composition Containing Soap, PolymericHydrogel Forming Polymer and High Level of Water" filed Sep. 16, 1994 inthe name of Trandai et al. is incorporated herein by reference in itsentirety for the purpose of disclosing gel forming agents.

Suitable soap gelling agents comprise monovalent-metal salts of fattyacids containing from about 12 to about 40 carbon atoms (C12-C40), andmore preferably C12-C22 salts of fatty acids. Suitable salt formingcations for use in these gelling agents include metal salts such asalkali metals, eg. sodium and potassium. In one embodiment the secondmaterial comprises a salt of fatty acids selected from the groupconsisting of sodium salts of fatty acids, potasium salts of a fattyacids, and combinations thereof.

Examples of fatty acids useful in synthesizing the soap gel formingagents include myristic, palmitic, stearic, oleic, linoleic, linolenic,margaric, and mixtures of such adds. Sources of such fatty acidsinclude, but are not limited to, coconut oil, beef tallow, lanolin, fishoil, beeswax, palm oil, peanut oil, olive oil, cottonseed oil, soybeanoil, corn oil, rapeseed oil, rosin acids, greases, castor oil, linseedoil, oiticica oil, neatsfoot, safflower oil, sesame oil, sorghum oil,sunflower oil, tall oil, tung oil, butter fat, poultry grease, whaleoil, and rice bran.

Preferred fatty add soap gel forming agents include sodium laurate,sodium myristate, sodium palmitate, sodium stearate, potassium laurate,potasium myristate, potasium palmitate, and potassium stearate. In oneembodiment the second material 2000 comprises a solution of sodiummyristate in water. A suitable solution comprises between about 5 andabout 30 percent by weight, and more preferably between about 5 andabout 20 percent by weight sodium myristate in water. Such a solutioncan have a gelling temperature of about 90-120 degrees Fahrenheit. Thesodium myristate can be formed by reacting myristic acid (C13H27COOH)with NaOH in water. The base and acid are added stoichiometrically toreact completely. The NaOH is added to the water and heated to about 180degrees Fahrenheit. The myristic acid is then gradually added to thewater/NaOH solution. The reaction is continued for about an hour. Thesodium myristate solution so formed is then cooled to about 140-160degrees Fahrenheit prior to application to the felt layer 220.

Such a solution of soap gelling agent and water has the advantage thatit can be solidified to a gel phase at a temperature between 50 degreesFahrenheit and about 150 degrees Fahrenheit prior to applying the resinto the substrate. The gel phase can thereby resist displacement of theliquid photosensitive resin at room temperature (about 70 degreeFahrenheit) without requiring refrigeration equipment to providesolidification. In addition, the solution is primarily water (at leastabout 70 percent water by weight when added to the felt layer 220).Accordingly, removal and disposal of the second material removed fromthe felt layer 220 is simplified, and environmental concerns areminimized.

Process for Forming a Continous Belt Having a Felt Layer and a PatternedResin Layer

FIG. 5 schematically illustrates a process according to one embodimentof the present invention for forming a web support apparatus 200 in theform of a continuous belt comprising a felt layer 220 having a curedresin layer 250. In the embodiment shown in FIG. 5, the felt layer 220can comprise an Amflex 2 felt commercially available from Appleton Millsof Appleton, Wis., and the photosensitive resin can comprise an MEH-1000resin commercially available from Hercules Chemical.

A forming unit 1513 in the form of a drum is provided having a workingsurface 1512. The forming unit 1513 is rotated by a drive means notillustrated. A backing film 1503 is provided from a roll 1531, and takenup by a roll 1532. Intermediate the rolls 1531 and 1532, the backingfilm 1503 is applied to the working surface 1512 of the forming unit1513. The function of the backing film is to protect the working surfaceof the forming unit 1513 and to facilitate the removal of the partiallycompleted web support apparatus 200 from the forming unit 1513. Thebacking film 1503 can be made of any suitable material including, butnot limited to, a film of polypropylene having a thickness of betweenabout 0.01 and about 0.1 millimeter.

As shown in FIG. 5, the felt dewatering layer 220 in the form of acontinuous belt is conveyed about forming drum 1513 and a number ofreturn rolls 1511 in a closed path. Prior to applying the secondmaterial and the liquid resin to the felt layer 220, the felt dewateringlayer 220 can be conveyed past an infrared heating lamp 2310 to preheatthe felt layer 220.

The felt layer 220 is then conveyed in a horizontal direction at a speedof about 1-10 feet/minute adjacent a pipe header 2410 containing thesecond material. The header 2410 has an opening through which the secondmaterial is deposited onto the second surface 232 of the felt layer 220.The opening in the header 2410 is positioned against the the secondsurface 232 of the felt layer 220. The second material directed from theheader 2410 is a solution of about 10 percent by weight sodium myristatein water having a temperature of about 120-150 degrees Fahrenheit.

About 0.9 grams of the second material per square inch of surface areaof the felt layer 220 is deposited on the felt layer 220. The felt layer220 on which the second material is deposited is then carried through anip 2470 between two rollers 2472. The spacing between the rollers 2472provides a nip which is about 0.010 inch less than the thickness of thefelt layer 220. The nip 2470 ensures distribution of the second materialthroughout the felt layer 220 and squeezes excess second material fromthe felt layer 220.

The second material deposited on the felt layer 220 is allowed to coolto a temperature of below about 90 degrees Fahrenheit to solidify thesecond material. Cooling the second material results in the formation ofstable gel phase of the sodium myristate in the voids of the felt layer220. After a stable gel phase of the second material has been formed,the felt layer 220 is conveyed adjacent to a water shower 2510 at aspeed of about 2-4 feet per minute. The water shower has nozzlespositioned about 3 inches from the first surface 230 of the felt layer220 for use in removal of some, but not all, of the gelled secondmaterial from the felt layer 220. The nozzles provide a plurality of fanshaped spray patterns arranged in overlapping fashion. The water showers2510 provide a water spray of about 1.5 gallons per square foot ofsurface area of the felt layer 220. The nozzles are Spray Systems TeeJet brand Nozzles, model 50015 having an orifice diameter of about 0.031inch. The water spray delivered by the showers 2510 has a temperature ofabout 90 degree Fahrenheit and is delivered to the nozzles at a pressureof about 500 psig.

The water shower 2510 is operated to remove second material adjacent thefirst surface 230, to thereby provide a portion of the thickness of thefelt layer 220 which is substantially free of the second material. Thewater showers 2510 can be used to remove a layer of the gelled secondmaterial having a thickness of between about 0.002 inch and about 0.2inch. The thickness of the layer of gelled second material removed isless than the thickness of the felt layer 220, such that between about75 percent and about 98 percent of the thickness of the felt layer 220remains impregnated with the gelled second material, and most preferablybetween about 85 percent and about 95 percent of the thickness of thefelt layer 220 remains impregnated with the gelled second material afterwashing with the water showers 2510. A vacuum header 2520 provides avacuum of about 1-4 psig at the first surface 230 of the felt layer 220to remove liquified second material and the water spray.

Once the first surface 230 of the felt layer 220 has been prepared byremoval of some, but not all of the second material from the felt layer220, the photosensitive resin can be applied to the first surface 230.The felt dewatering layer 220 is positioned adjacent the backing film1503 such that backing film 1503 is interposed between the feltdewatering layer 220 and the forming unit 1513, and such that the secondfelt surface 232 of the felt dewatering layer 220 is positioned adjacentthe backing film 1503. A coating of liquid photosensitive resin isapplied to the first felt surface 230. The coating of liquidphotosensitive resin 1502 can be applied to the first felt surface inany suitable manner. In FIG. 5 the coating of resin is applied by anozzle 1520 to form a pool of resin on the the felt layer 220 upstreamof a nip formed by nip roll 3100.

The thickness of the coating of resin applied to the felt layer 220 iscontrolled to a preselected value corresponding to the desireddifference in elevation 262 between the elevation of the first feltsurface 230 and the elevation of the web contacting top surface 260 ofthe web patterning layer 250. In FIG. 5, the thickness of the coating ofresin is controlled by mechanically controlling the clearance between anip roll 3100 and the forming unit 1513. The nip roll 3100 inconjunction with the mask 3010 and a mask guide roll 1542 tend to smooththe surface of the resin and control its thickness. The gelled secondmaterial prevents the liquid photosensitive resin from penetratingthroughout the portion of the thickness of felt layer 220 occupied bythe gelled second material.

The mask 3010 can be formed of any suitable material which can beprovided with opaque and transparent portions. The transparent portionsare arranged in a pattern corresponding to the desired pattern of theweb patterning layer 250. A material in the nature of a flexiblephotographic film is suitable. The opaque portions can be applied to themask 3010 in any suitable way, such as photographic, gravure,flexographic, or rotary screen printing. The mask 3010 can be an endlessbelt, or alternatively, supplied from one supply roll 3012 and taken upby a take-up roll 3016, as shown in FIG. 5. As shown in FIG. 5, the mask3010 is conveyed around the rolls 3100, 1542, 3014, and 3016.Intermediate the rolls 3100 and 1542, the mask 3010 travels with thefelt layer 220 around the forming unit 1513, and is positioned adjacentthe liquid resin, with the mask intermediate the resin and a source ofactinic radiation which is suitable for curing the liquid resin.

The photosensitive resin is exposed to actinic radiation of anactivating wavelength through the mask 3010, thereby inducing at leastpartial curing of the resin in those portions of the layer of resinwhich are in register with transparent portions of the mask 3010. InFIG. 5, ultraviolet radiation having an activating wavelength issupplied by first curing lamps 3150. The activating wavelength is acharacteristic of the resin, and can be supplied by any suitable sourceof illumination such as mercury are, pulsed xenon, electrodless, andfluorescent lamps. For the MEH-1000 resin, suitable curing lamps 3150are F450 Fusion Lamps fitted with "D" or "H" bulbs, and commerciallyavailable from Fusion Systems, Inc. of Rockville, Md. The felt layer 220can be conveyed adjacent the curing lamps 3150 at a speed of about 1-3feet/minute during casting.

Partial curing of the resin is manifested by a solidification of theresin registered with the transparent portions of the mask 3010, whilethe unexposed potions of the resin registered with the opaque potions ofthe mask 3010 remain liquid. To obtain a uniform initial curing of theresin on the felt layer 220, the energy provided by the UV light to thephotosensitive resin should be uniform across the width of the feltlayer 220. Output from each of the curing lamps 3150 should be matchedto be within at least about 5 percent of each other. The curing lamps3150 can be positioned side by side in the cross-machine direction(perpendicular to the plane of FIG. 5.) For example, three curing lamps3150 can be positioned side by side in the machine direction. A pair ofaperture plates are disposed intermediate the lamps 3150 and the feltlayer 220, and are spaced apart in the machine direction to form anaperture gap through which ultraviolet light is directed from the lamps3150 to the resin pooled on the felt layer 220.

Total energy directed to the felt layer 220 can be measured by a "lightbug" such as the EIT UV Integrating Radiometer, Model Number UR365CH1made by Electronic Instrumentation Technologies located in Stifling Va.The light bug can be fastened to the casting drum 1513 to measure theintegrated energy in millijoules per square centimeter applied to thefelt layer 220. By repeating this measurement every 1/2 inch across thewidth of the drum 1513, a profile of the energy imparted from the lamps3150 to the photosensitive resin can be determined. If the gap betweenthe aperture plates is uniform along the width of the drum 1513, theenergy profile will generally not be uniform. The gap between theaperture plates can be varied as a function of position in thecross-machine direction to provide a uniform energy profile delivered bythe lamps 3150 to the resin pooled on the felt layer 220.

After partially curing the resin layer applied to the first surface 230,substantially all the uncured liquid resin can be removed from the feltdewatering layer 220. The uncured liquid resin can be removed from thefelt layer 220 by high pressure showering of the felt layer 220 withwater, or alternatively, a mixture of surfactant and water. At a pointadjacent the roll 1542 the mask 3010 and the backing film 1503 areseparated from the felt layer 220 and the partially cured resin layer.The composite felt layer 220 and partially cured resin layer areconveyed adjacent water showers 2530. The water showers 2530 can beangled to remove uncured resin 2010A from the openings in the patternedresin layer.

The showers 2530 deliver a spray at a temperature of about 60-80 degreesFahrenheit through nozzles such as Spray Systems Tee Jet brand Nozzles,model 50015, having an orifice diameter of about 0.031 inch. The showerdelivery pressure is about 500 psig. The showers 2530 and the felt layer220 can be moved laterally (perpendicular to the plane of FIG. 5)relative to one another to eliminate streaking and provide uniformremoval of the liquid resin across the width of the felt layer 220.

The composite felt layer 220 and resin layer can then be carried througha bath 1620 of distilled or deionized water. At this point, the gelledsecond material is still present in the second felt layer 220. Post curelamps 3180 positioned over the bath 1620 are turned off while thecomposite felt layer 220 and resin layer is carried through the bath1620 for the first time. The post cure lamps are turned on in a finalcuring step described below.

After leaving the bath 1620, the composite felt layer 220 and resinlayer is carried intermediate infrared heating lamps 3170 and a vacuumheader 2560 at a speed of about 1-3 foot per minute. The heating lamps3170 heat the gelled second material to a temperature of about 140degrees Fahrenheit, which is above the gelling temperature of the secondmaterial, so that substantially all of the second material is liquifiedfor removal from the felt layer 220. The heating lamps 3170 arepositioned adjacent the first felt surface 230, and the vacuum header2560 is positioned adjacent the second felt surface 232. The heatinglamps 3170 can be positioned about 3 inches from the felt layer 220. Asuitable infrared heating lamp 3170 is a Protherm heating lampmanufactured by the Process Thermal Company, and having a power ratingof about 20 amps. The vacuum header 2560 provides a vacuum of about 1-5psig at the second felt surface 232.

The composite felt layer and resin layer is then conveyed intermediatehot water showers 2550 and a vacuum header 2570. The hot water shower2550 directs a spray against the first surface 230 of the felt layer220. The showers 2550 deliver the a distilled water spray at atemperature of about 140 degrees Fahrenheit using Tee Jet brand Nozzles.The shower delivery pressure is about 50-200 psig. The vacuum header2570 provides a vacuum of about 1-5 psig at the second surface 232 ofthe felt layer 220 to remove liquified second material and any remaininguncured liquid resin from the second surface 232.

Preferably substantially all of the second material is removed from thefelt layer 220 by the heat lamps 3170, water showers 2550, and vacuumheaders 2560 and 2570. If desired, the composite felt layer 220 andresin layer can be conveyed around the closed path defined by roller1513 and rollers 1511 for multiple passes through the heat lamps 3170,water showers 2550, and vacuum headers 2560 and 2570. It will beunderstood that if the composite felt layer 220 and resin layer iscarried around the closed path multiple times to remove the secondmaterial from the felt layer 220, the multiple passes are made withoutadding more second material or or liquid resin to the felt layer 220,and with the ultraviolet lamps 3150 and 3180 turned off

The web support apparatus 200 can be inspected with a microscope toverify that all the uncured liquid resin and second material have beenremoved from the felt layer 220. Alternatively, the cleanliness of thefelt layer 220 can be measured using a drainage test as follows. The websupport apparatus 200 can be positioned between between upper and lowerPlexiglas orifice plates having 3.25 inch openings. The upper orificeplate is joined to an upstanding cylinder having an internal diameter ofabout 4 inches. Distilled water is added to the cylinder to maintain acolumn of water about 4 inches high in the cylinder. The volume of waterpassing through the apparatus 200 is measured for a drainage time of 1minute. The drainage rate (cubic centimeters/sec/square foot) of the websupport apparatus 200 should be generally uniform when measured atdifferent locations on the web support apparatus 200, and should be atleast about equal to the drainage rate of the felt layer 220 multipliedby the fraction of the projected area of the apparatus 200 not coveredby the web patterning layer 250.

A final step in practicing the present invention can include a secondpost curing step for completing curing of the resin layer on the firstsurface of the felt layer 220. Once substantially all the secondmaterial and all the uncured liquid resin have been removed from thefelt layer 220, the composite felt layer 220 and resin can be conveyedthrough the bath 1620. Post curing lamps 3180 positioned above the bath1620 provide final curing of the resin layer. The composite felt layer220 and resin layer are submerged in the bath 1620 which preferablycontains water and a reducing agent, such as sodium sulfite, to removedissolved oxygen in the water which would otherwise quench the freeradical curing reaction in the bath 1620.

The composite felt layer 220 and resin layer 250 are carried through thebath 1620 at a speed of about 1-3 feet per minute with the post curinglamps 3180 turned on. Suitable post curing lamps 3180 are the F450 lampslisted above. The water in the bath 1620 permits passage of the actinicradiation from the post curing lamp 3180 to the resin layer 1521, whileprecluding oxygen which can quench the free radical polymerizationreaction. The water depth in the bath 1620 can be about 1-4 inches.After exiting the bath 1620, the composite felt layer 220 and resinlayer 250 (FIG. 4H) can be carried over a vacuum header to remove waterfrom the felt layer 220.

The post curing sequence of passing the composite felt layer 220 andresin layer through the bath 1620 with the post curing lamp 3180 turnedon can be repeated about 1 to 3 times until the resin layer 250 is nolonger tacky. At this point, the felt layer 220 and the cured resin,together, form the web support apparatus 200 having a fully cured webpatterning layer 250. The post curing sequence can be repeated bycarrying the composite felt layer 220 and resin layer around the circuitprovided by the rollers 1513 and 1511 one to three times with the lamp3150 turned off.

In one embodiment, the mask 3010 can be provided with a transparentportion in the form a continuous network. Such a mask can be used toprovide the web support apparatus 200 having a web patterning layer 250having a continuous network web contacting top surface 260 having aplurality of discrete openings 270 therein, as shown in FIG. 1. Eachdiscrete opening 270 communicates with the first felt surface 230through a conduit formed in the web patterning layer 250. Suitableshapes for the openings 270 include, but are not limited to circles,ovals elongated in the machine direction (MD shown in FIG. 5), polygons,irregular shapes, or mixtures of these. The projected surface area ofthe continuous network top surface 260 can be between about 5 and about75 percent of the projected area of the web support apparatus 200 asviewed in FIG. 1, and is preferably between about 20 percent and about60 percent of the projected area of the web support apparatus 200 asviewed in FIG. 1.

In the embodiment shown in FIG. 1, the continuous network top surface260 can have less than about 700 discrete openings 270 per square inchof the projected area of the web support apparatus 200, and preferablybetween about 70 and about 700 discrete openings 270 therein per squareinch of projected area of the web support apparatus as viewed in FIG. 1.Each discrete opening 270 in the continuous network top surface can havean effective free span which is between about 0.5 and about 3.5millimeter, where the effective free span is defined as the area of theopening 270 divided by one-fourth of the perimeter of the opening 270.The effective free span can be between about 0.6 and about 6.6 times theelevation difference 262. An apparatus having such a pattern of openings270 can be used as a drying belt or press fabric on a papermakingmachine for making a patterned paper structure having a continuousnetwork region which can be a compacted, relatively high density regioncorresponding to the web contacting surface 260, and a plurality ofgenerally uncompacted domes dispersed domes dispersed throughout thecontinuous network region, the domes corresponding to the positioning ofthe openings 270 in the surface 260. The discrete openings 270 arepreferably bilaterally staggered in the machine direction (MD) andcross-machine direction (CD) as described in U.S. Pat. No. 4,637,859issued Jan. 20, 1987, which patent is incorporated herein by reference.In the embodiment shown in FIG. 1, openings 270 are over-lapping andbilaterally staggered, with the openings sized and spaced such that inboth the machine and cross-machine directions the edges of the openings270 extend past one another, and such that any line drawn parallel toeither the machine or cross-machine direction will pass through at leastsome openings 270.

Measurement of Web Support Apparatus Elevations

The elevation difference 262 between the elevation 231 (FIG. 2) of thefirst felt surface 230 and the elevation 261 of the web contactingsurface 260 is measured using the following procedure. The web supportapparatus is supported on a flat horizontal surface with the webpatterning layer facing upward. A stylus having a circular contactsurface of about 1.3 square millimeters and a vertical length of about 3millimeters is mounted on a Federal Products dimensioning gauge (model432B-81 amplifier modified for use with an EMD-4320 W1 breakaway probe)manufactured by the Federal Products Company of Providence, R.I. Theinstrument is calibrated by determining the voltage difference betweentwo precision shims of known thickness which provide a known elevationdifference. The instrument is zeroed at an elevation slightly lower thanthe first felt surface 230 to insure unrestricted travel of the stylus.The stylus is placed over the elevation of interest and lowered to makethe measurement. The stylus exerts a pressure of 0.24 grams/squaremillimeter at the point of measurement. At least three measurements aremade at each elevation. The difference in the average measurements ofthe individual elevations 231 and 261 is taken as the elevationdifference 262.

FIGS. 6 and 7 are photomicrographs of a web support apparatus 200 madeaccording to the present invention. The web support apparatus 200 inFIGS. 6 and 7 comprises a resin layer 250 cured on a dewatering feltlayer 220. The cured resin layer 250 penetrates a surface 230 of thefelt layer 220, such that the cured resin layer extends into a portionof the thickness of the felt layer adjacent to the surface 230. Thecured resin layer 250 also extends from the 230, such that the surface260 of the resin layer is spaced from the surface 230.

In the embodiments described above, the substrate comprises a dewateringfelt layer 220. However, the method of the present invention can also beused to form patterned resin layers on other substrates. For example,the substrate can comprise a papermaking forming or drying fabriccomprising woven filaments, which fabric can have an air permeability ofbetween about 300 and about 1,500 scfm. A non-limiting example of analternative substrate is a papermachine fabric described in thefollowing U.S. Patents issued to Trokhan and incorporated herein byreference: U.S. Pat. No. 4,191,609 issued Mar. 4, 1980 and U.S. Pat. No.4,239,065 issued Dec. 16, 1980.

What is claimed:
 1. A method of applying a photosensitive resin to asubstrate to form an apparatus for use in papermaking, the methodcomprising the steps of:providing a substrate having a first surface, asecond surface, and a thickness, the substrate having voids intermediatethe first and second surfaces; providing a liquid photosensitive resin;providing a second material different from the liquid photosensitiveresin; providing a source of actinic radiation; applying the secondmaterial to the substrate to occupy at least some of the voids in thesubstrate intermediate the first and second surfaces of the substrate;removing at least some, but not all, of the second material from thesubstrate before applying the liquid photosensitive resin to thesubstrate; applying the liquid photosensitive resin to the substrate tooccupy at least some of the voids in the substrate; exposing at leastsome of the liquid photosensitive resin to the actinic radiation; andcuring at least some of the photosensitive resin to provide a patternedresin layer disposed on the first surface of the substrate.
 2. Themethod of claim 1 further comprising the step of substantially changingthe viscosity of at least some of the second material applied to thesubstrate before the step of curing the resin.
 3. The method of claim 1further comprising the step of removing at least some of the secondmaterial from the substrate after applying the resin to the substrate.4. The method of claim 1 further comprising the step of changing thephase of at least some of the second material applied to the substratebefore the step of curing the resin.
 5. The method of claim 1 furthercomprising the step of solidifying at least some of the second materialapplied to the substrate at a temperature between about 50 degreesFahrenheit and about 150 degrees Fahrenheit prior to applying the resinto the substrate.
 6. The method of claim 1 further comprising the stepof cooling at least some of the second material applied to the substratebefore the step of curing the resin, and the step of heating at leastsome of the second material applied to the substrate before a step ofremoving second material from the substrate.
 7. The method of claim 1wherein the second material comprises water.
 8. The method of claim 1wherein the second material comprises a component which is soluble inwater.
 9. The method of claim 1 wherein the second material comprises asolvent and a solute.
 10. The method of claim 1 wherein the secondmaterial comprises a surfactant.
 11. The method of claim 1 wherein thesecond material comprises an alcohol.
 12. The method of claim 1 whereinthe second material comprises a component selected from the groupconsisting of glycerol, polyoxyethylene glycol, polyoxypropylene glycol,and combinations thereof.
 13. The method of claim 1 wherein the secondmaterial comprises a gelling agent.
 14. The method of claim 13 whereinthe second material comprises a soap gelling agent.
 15. The method ofclaim 1 wherein the second material comprises a salt of fatty acidscontaining from about 12 to about 22 carbon atoms.
 16. The method ofclaim 1 wherein the second material comprises a salt of fatty acidsselected from the group consisting of sodium salts of fatty acids,potasium salts of a fatty acids, and combinations thereof.
 17. Themethod of claim 1 wherein the second material comprises a gel formingagent selected from the group consisting of sodium laurate, sodiummyristate, sodium palmitate, sodium stearate, potassium laurate,potassium myristate, potassium palmitate, potassium stearate, andmixtures thereof.
 18. A method of applying a photosensitive resin to asubstrate to form an apparatus for use in papermaking, the methodcomprising the steps of:providing a substrate having a first surface, asecond surface, and a thickness, the substrate having voids intermediatethe first and second surfaces; providing a liquid photosensitive resin;providing a second material different from the liquid photosensitiveresin; providing a source of actinic radiation; providing a maskcomprising regions opaque to the radiation and regions transparent tothe radiation; applying the second material to the substrate to occupyat least some of the voids in the substrate intermediate the first andsecond surfaces of the substrate; providing a portion of the thicknessof the substrate adjacent the first surface of the substrate which issubstantially free of the second material; applying the liquidphotosensitive resin to the first surface of the substrate to occupy atleast some of the voids in the portion of the thickness of the substratewhich is substantially free of the second material; positioning the maskintermediate the source of radiation and the coating of liquidphotosensitive resin; and exposing liquid photosensitive resin to theactinic radiation through the mask to induce curing of photosensitiveresin in registration with the transparent regions in the mask toprovide a patterned resin layer disposed on the first surface of thesubstrate.
 19. The method of claim 18 wherein the substrate comprises apapermaker's dewatering felt.
 20. A method of applying a photosensitiveresin to a substrate to form an apparatus for use in papermaking, themethod comprising the steps of:providing a substrate having a firstsurface, a second surface, and a thickness, the substrate having voidsintermediate the first and second surfaces; providing a liquidphotosensitive resin; providing a second material different from theliquid photosensitive resin; providing a source of actinic radiation;providing a mask comprising regions opaque to the radiation and regionstransparent to the radiation; applying the second material to thesubstrate to occupy at least some of the voids in the substrateintermediate the first and second surfaces of the substrate; removingsome, but not all, of the second material from the substrate prior toapplying the liquid photosensitive resin to the substrate, to provide aportion of the thickness of the substrate adjacent the first surface ofthe substrate which is substantially free of the second material;applying the liquid photosensitive resin to the first surface of thesubstrate; positioning the mask intermediate the source of radiation andthe coating of liquid photosensitive resin; exposing the liquidphotosensitive resin to the actinic radiation through the mask to inducecuring of the photosensitive resin in registration with the transparentregions in the mask to provide a patterned resin layer on the firstsurface of the substrate; removing at least some uncured photosensitiveresin and second material from the substrate after curing photosensitiveresin in registration with the transparent regions in the mask; and postcuring the photosensitive resin after removing substantially all of thesecond material from the substrate.
 21. A method of applying aphotosensitive resin to a papermakers dewatering felt, the methodcomprising the steps of:providing a papermakers dewatering felt having afirst surface, a second surface, and a thickness, the papermakersdewatering felt having voids intermediate the first and second surfaces;providing a liquid photosensitive resin; providing a second materialdifferent from the liquid photosensitive resin; providing a source ofactinic radiation; applying the second material to the papermakersdewatering felt to occupy at least some of the voids in the papermakersdewatering felt intermediate the first and second surfaces of thepapermakers dewatering felt; applying the liquid photosensitive resin tothe papermakers dewatering felt; exposing at least some of the liquidphotosensitive resin to the actinic radiation; and curing at least someof the photosensitive resin to provide a patterned resin layer disposedon the first surface of the papermakers dewatering felt.
 22. The methodof claim 21 further comprising the step of providing a portion of thethickness of the felt adjacent the first surface of the felt which issubstantially free of the second material before applying the resin tothe felt.
 23. The method of claim 22 wherein the step of providing aportion of the thickness of the felt adjacent the first surface which issubstantially free of the second material comprises removing some, butnot all, of the second material from the felt before applying the resinto the felt.
 24. The method of claim 21 further comprising the stepsof:solidifying at least some of the second material applied to the feltbefore applying resin to the felt; and removing some, but not all, ofthe second material from the felt before applying resin to the felt. 25.The method of claim 21 wherein the papermakers dewatering felt comprisesa fibrous batt, wherein the step of applying the second material to thedewatering felt comprises applying the second material to the fibrousbatt to occupy at least some voids in the fibrous batt, and wherein thestep of applying the photosensitive resin to the dewatering feltcomprises applying the resin to the fibrous batt.